Mechanistic aspects of electrochemical hydride generation for cadmium.
ABSTRACT The mechanistic aspects of a novel methodology for the electrochemical hydride generation (EcHG) of cadmium, entitled as the catholyte variation, have been studied. The hydrogen overvoltage of different cathode materials was determined in dilute electrolyte. The lead-tin alloy used as the cathode material for the EcHG of Cd had the highest hydrogen overpotential. In this technique, both electrolyte medium and cathode surface would change during electrolysis. The catholyte variation EcHG coupled with a flame heated quartz tube atomizer (QTA) atomic absorption spectrometer (AAS) produced peak-shaped transient signal of Cd. The analytical signal was significantly enhanced at neutralization time. The simultaneous production of lead and tin hydrides as well as the hydrogen at that time may speed up the desorption of cadmium species from the surface of the cathode. Also the high hydrogen overvoltage and the neutral medium aided the formation and separation of cadmium hydride molecules. The generated CdH2 vapour was kinetically stable.
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ABSTRACT: A simple method was developed for speciation and spectrophotometric determination of inorganic As(III) and As(V) using an electrochemical hydride generation technique. For speciation of As(III) and As(V), a graphite rod was used as cathode to reduce As(III) to AsH(3), the rod was then replaced with a tin-lead alloy wire for reducing As(V) to AsH(3). The spectrophotometric determination was based on the reaction of AsH(3) with silver diethyldithiocarbamate to give an absorbing complex at 510 nm. Under the optimized conditions, the calibration curves were linear over the ranges of 0.1-5 microg ml(-1) for As(III) and 0.5-4.0 microg ml(-1) for As(V). The concentration detection limits of 0.02 and 0.06 microg ml(-1) were achieved for As(III) and As(V), respectively. The relative standard deviations for five replicate speciation and determination of 3.0 microg ml(-1) As(III) and As(V) were 0.8 and 7.2%, respectively. The accuracy and recovery of the method were evaluated by analyzing tap water spiked with As(III) and As(V).Analytical Sciences 01/2010; 26(1):107-10. · 1.57 Impact Factor
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ABSTRACT: A novel electrochemical hydride generation (ECHG) system working in flow-injection (FI) mode was developed for determination of cadmium coupled to an electrically heated quartz tube atomizer (QTA) by atomic absorption spectrometry (AAS). A Plackett-Burman experimental design for screening has been used to evaluate the influence of several variables on the analytical response. Then, the significant parameters such as the concentration of NaCl in catholyte, applied electrolytic current and flow rate of carrier gas have been simultaneously optimized using a central composite design (CCD). Under the optimized conditions, the detection limit (3σ(b), n=9) was found to be 0.51 ng mL(-1) Cd and the relative standard deviation (RSD) for nine replicate analyses of 20 ng mL(-1) Cd was 6.5%. The calibration curve was linear in the range of 2-50 ng mL(-1) of Cd. The potential interferences from various ions were also evaluated. The analysis of a reference material showed good agreement with the certified value. The proposed method was successfully applied to the determination of Cd in tap water sample.Talanta 08/2012; 97:229-34. · 3.50 Impact Factor
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ABSTRACT: Chemical vapor generation (CVG) using tetrahydroborate(III) remains the most popular and successful derivatization procedure enabling gaseous sample introduction into analytical atomic spectrometers that are routinely used for the determination of trace and ultratrace amounts of hydride-forming elements as well as Cd and Hg. The number of elements amenable to tetrahydroborate(III)-derivatization has recently been extensively enlarged. Despite its many obvious advantages, drawbacks remain, such as significant interferences from transition metals. Consequently, many alternative approaches have been developed to overcome these shortcomings and to further expand the suite of elements amenable to CVG for sample introduction. This article reviews these non-tetrahydroborate-based approaches, including photochemical vapor generation (photo-CVG), borane complexes CVG, alkylation based on Grignard reactions and derivatization with NaBEt4, cold vapor generation with SnCl2, halide generation, electrochemical hydride generation, oxide generation, and generation of volatile chelates. Special attention is given to two newly developed CVG approaches: photo-CVG and reduction in the presence of cyanoborohydrides.Journal of Analytical Atomic Spectrometry 01/2010; 25(8). · 3.40 Impact Factor